def addTwoNumbers(self,l1,l2):
	head = ListNode(0)
	l = head
	carry = 0
	while l1 or l2 or carry:
		sum,carry = carry,0
		if l1:
			sum += l1.val
			l1 = l1.next
		if l2:
			sum+=l2.val
		if sum > 9:
			carry = 1
			sum -= 10
		l.next =ListNode(sum)
		l = l.next
	return head.next

addTwoNumbers((2 -> 4 -> 3) + (5 -> 6 -> 4))